1. INTERNATIONAL SYMPOSIUM ON ELECTRONICS AND TELECOMMUNICATIONS ETC 2010 NINTH EDITION A PHYSICAL LAYER SIMULATOR FOR WIMAX Marius Oltean, Maria Kovaci, Alexandru Isar, Jamal Mountassir, Petru Laz ă r

2. Outline  Introduction  PHY layer in WiMAX  PHY layer simulator  Simulation results  Conclusions

3. Introduction  WiMAX: a powerful candidate for 4 th generation of mobile communication systems, based on IEEE 802.16e.  MAC layer is oriented on the QoS.  PHY layer relies on OFDMA technique.  DL/UL separation by FDD and TDD techniques.

4. PHY layer  OFDM symbol:  OFDM/OFDMA implementations are based on the IFFT and FFT techniques.  Two types of permutation are used: PUSC and FUSC.  AMC: reduces the complexity and is well suited for the channels that change slowly in time

5. MAC layer  for DL FUSC and PUSC, the pilot tones are allocated first. The remaining data subcarriers are divided into subchannels that are used exclusively for data  For UL PUSC, the set of used subcarriers is first partitioned into subchannels and then the pilot subcarriers are allocated from within each subchannel. Fig. 1: WiMAX radio frame (TDD).

6. DL-PUSC Fig. 2 : Segment 0 composition and pilot subcarriers for DL-PUSC 512.

7. Channel Coding Techniques  Convolutional coding ;  Turbo-coding;  LDPC coding;  Convolutional turbo-coding (CTC) Fig 3. Logical resources for DL-PUSC

8. PHY Layer Simulator Fig 4. The block scheme of the WiMAX simulator

9. Simulation Results  computation of BER and BLER statistics;  QPSK, 16QAM;  AWGN channel.

10. UL-PUSC 512  QPSK is better than 16 QAM but the communication is slower. Fig. 5: BER performance: UL-PUSC 512.

11. DL- FUSC 512  The strength of the turbo- codes leads to very good BER results.  Consequently: at 2dB the BER is already below 0.0001.  For BER=0.001, the gain of QPSK versus 16QAM is approximately 3.5 dB. Fig. 6: BER performance for DL- FUSC 512.

12. CONCLUSIONS  Better understanding of the signal processing steps at the PHY layer of IEEE 802.16e specifications.  Performance evaluation in different scenarios  A realistic model take into account the time variability and the frequency selectivity.

13. FURTHER WORK  The future improvements will cover some "gaps“ in our simulator.  The decoder for 64QAM is not yet implemented.  The implemented permutation types may be extended to the adjacent case too since presently only the distributed permutations are simulated.

14. References [1] J. Yun and M. Kavehrad, ”PHY/MAC Cross-Layer issues in Mobile WiMAX.”, Bechtel Telecommunications Technical Jan. 2006, pp. 45-56. [2] H. Yaghoobi, "Scalable OFDMA Physical Layer in IEEE 802.16 Wireless MAN", Intel Technology Journal, Vol.1, Issue3,2004, pp. 201-212. [3] H. Balta, D. Bosneagu, M. Kovaci, M. Oltean "A Study of the Permutation Schemes Used in the Mobile WIMAX", Acta Technica Napocensis – Electronics and Telecommunications, Volum 29,Nr.3/2008, pp.17-20. [4] WiMAX Forum Applications Working Group, "System design and AWGN Results", 2008. [5] C. Douillard, and C. Berrou, ”Turbo Codes with Rate-m/(m+1) Constituent Convolutional Codes”, IEEE Transactions on Communications, Vol. 53, No. 10, Oct. 2005, pp.1630-1638. [6] J. Vogt and A. Finger, “Improving the max-log-MAP turbo decoder”, Electron. Lett., vol. 36, no. 23, pp. 1937–1939, Nov.2000. [7] H. Balta, C. Douillard, and M. Kovaci, “The Minimum Likelihood APP Based Early Stopping Criterion for Multi-Binary Turbo Codes”, Proc. of. Symposium of Electronics and Telecommunications – ETc 2006, Timisoara, Sept. 2006, pp.199- 203.